Check for scheduled event to prevent duplicates

[markparolisi]

wp_schedule_event() checks if the interval (hourly, daily, etc) of the event is valid, but it does not check if the event is already scheduled.
A simple check of the cron array should return false if the event already exists.
This will prevent crippling DB queries resulting from endless duplication of scheduled events

[scribu]

I agree that it's a good idea to prevent multiple recurring events with the same callback to be scheduled.

[scribu]

check wp_next_scheduled()

[scribu]

jgadbois, that won't work, since $timestamp will be different most of the time.

The correct way is to use wp_next_scheduled(). See 14668.2.diff

[scribu]

The problem with 14668.2.diff is that it doesn't allow scheduling non-regular intervals.

For example, if I want to schedule the same event to run twice daily, but on specific hours, I can currently do this:

if ( !wp_next_scheduled( 'my_event' ) ) {
  wp_schedule_event( strtotime( '10am' ), 'daily', 'my_event' );
  wp_schedule_event( strtotime( '12am' ), 'daily', 'my_event' );
}

[scribu]

(In [16690]) Add note about wp_next_scheduled() in wp_schedule_event(). See #14668